<!DOCTYPE html>
<html>
<head>
<style type="text/css">
#a {
 height: 20px;
 background-color: green;
 margin-bottom: 20px;
}
#b {
 background-color: red;
 padding-top: 10px;
}
#c {
 background-color: green;
 padding-top: 20px;
}
#d {
 height: 20px;
 background-color: blue;
}
</style>
</head>
<body>
<div id="a"></div>
<div id="b">
 <div id="c">
  <div id="d"></div>
 </div>
</div>
</body>
</html>
